Many processes have been proposed for the removal of acidic gases such as, for example, carbon dioxide, sulfur dioxide, hydrogen sulfide and the like from mixed gas streams. One particularly successful and widely employed process for the removal of these acidic gases is the so-called "Girbotol Amine Process." This process has been employed to provide for both the removal and recovery of carbon dioxide from flue gases (see Kirk-Othmer, Encyclopedia of Chemical Technology, Vol. 4, 2ed (1969) page 362) as well as to sweeten natural gases (id., Vol. 1, pages 821-822). A more complete and detailed description of this process can be found in U.S. Pat. No. Re. 18,985, issued Sept. 26, 1933.
Broadly, the "Girbotol Amine Process" can be considered a two-step process where in the first step the mixed qas feed stream containinq the acidic gases is contacted with an alkanolamine or alkanolamine solution in a suitable absorption zone. This contact is effected over a range of operating conditions of temperature and pressure. The particular conditions employed for this contact will depend upon the nature of the mixed gas stream undergoing treatment, the alkanolamine employed, whether the purpose is the recovery of acidic gases contained in the mixed gas stream or merely to sweeten the mixed gas stream and the like. In this regard, operating conditions such as temperatures of from about 80.degree. F. (26.degree. C.) to about 150.degree. F. (65.degree. C.) and pressures of from atmospheric to about 1000 psi (70.3 kg/sq.cm.) have been employed in carrying out the first step of the process (see Kirk-Othmer, Encyclopedia of Chemical Technology. Vol. 1, 2Ed, (1969) page 822). Under these conditions the acidic gases combine with the alkanolamine to form acidic gas/alkanolamine products which are soluble in the alkanolamine and thereby are removed from the mixed gas stream undergoing treatment.
In the second step of the process, the acidic gas/alkanolamine products are withdrawn from the absorption zone and introduced into a suitable alkanolamine or alkanolamine solution regeneration zone. Within this regeneration zone, the acidic gas/alkanolamine products produced in the absorption zone are decomposed with the simultaneous regeneration of the individual acidic gases and the alkanolamine or alkanolamine solution. This regeneration step is carried out by heating the acidic gas/alkanolamine products to significantly higher temperatures than those employed in the first (or absorption) step of the process. The temperatures most usually employed in this second step will range from about 220.degree. F. (104.degree. C.) to 240.degree. F. (115.degree. C.). The regenerated alkanolamine or alkanolamine solution is returned to the absorption zone, after cooling, wherein it is employed to treat further quantities of the mixed gas stream. The acidic gases can be discarded or, in the case of carbon dioxide, recovered for further processing.
In general, faoilities utilizing the above described process are designed and constructed around predetermined operating conditions. Such conditions include the nature and make-up of the mixed gas feed stream to be treated, the alkanolamine to be employed and when employed in solution its concentration, the temperatures, pressures, and the like. Once these operating conditions are established the appropriate size equipment required for the facility readily can be determined. However, once constructed, the maximum capacity for such facilities is relatively fixed and cannot be increased without a major reconstruction of the facilities. Thus, any improvements in the above described process which can increase the removal of acidic gases in a gaseous stream without a major reconstruction of facilities based on such process would constitute a significant advancement in this art.